Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters

Show simple item record Purchase, Cromwell Napier, Kathryn R. Nicolson, Sue W. McWhorter, Todd J. Fleming, Patricia A. 2013-06-12T07:16:24Z 2013-06-12T07:16:24Z 2013
dc.description.abstract Nectarivores face a constant challenge in terms of water balance, experiencing water loading or dehydration when switching between food plants or between feeding and fasting. To understand how whitebellied sunbirds and New Holland honeyeaters meet the challenges of varying preformed water load, we used the elimination of intramuscular-injected [14C]-L-glucose and 3H2O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both sunbirds and honeyeaters showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine when on dilute diets. Despite reducing their fractional water absorption, both species showed linear increases in water flux and fractional body water turnover as water intake increased (both afternoon and morning), suggesting that the modulation of fractional water absorption was not sufficient to completely offset dietary water loads. In both species, glomerular filtration rate was independent of water gain (but was higher for the afternoon), as was renal fractional water reabsorption (measured in the afternoon). During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function. Evaporative water loss in sunbirds was variable but correlated with water gain. Both sunbirds and honeyeaters appear to modulate intestinal water absorption as an important component of water regulation to help deal with massive preformed water loads. Shutting down glomerular filtration rate during the overnight fast is another way of saving energy for osmoregulatory function. Birds maintain osmotic balance on diets varying markedly in preformed water load by varying both intestinal water absorption and excretion through the intestine and kidneys. en
dc.description.librarian am2013 en
dc.description.librarian ab2013
dc.description.sponsorship This project was funded by the National Research Foundation of South Africa, the University of Pretoria and the Australian Research Council (DP0665730). en
dc.description.uri en
dc.identifier.citation Purchase, C, Napier, KR, Nicolson, SW, McWhorter, TJ & Fleming, PA 2013, 'Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters', Journal of Experimental Biology, vol. 216, no. 9, pp. 1537-1545. en
dc.identifier.issn 0022-0949 (print)
dc.identifier.issn 1477-9145 (online)
dc.identifier.other 10.1242/jeb.075176
dc.language.iso en en
dc.publisher Company of Biologists en
dc.rights © 2013. Published by The Company of Biologists Ltd en
dc.subject Water balance en
dc.subject Osmoregulation en
dc.subject Intestinal water absorption en
dc.subject Renal function en
dc.subject Nectarivore en
dc.subject.lcsh Sunbirds en
dc.subject.lcsh Honeyeaters en
dc.subject.lcsh Passeriformes en
dc.subject.lcsh Water in the body en
dc.subject.lcsh Body fluids en
dc.subject.lcsh Pharmacokinetics en
dc.title Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters en
dc.type Article en

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